Tubular air preheater for steam generator units and the like



March 14, 1950 J. v'. PYLE 2,500,771

TUBULAR AIR PREHEATER FOR STEAM GENERATOR UNITS AND THE LIKE 2Sheets-Sheet 1 Filed Sept. 4, 1946 INVENTOR JO/l/V u m: BY 7 vZMM'@71I-Z-w will? ATTO R N EYS March 14, 1950 J. v. PYLE 2,500,771

" TUBULAR AIR PREHEATER FOR STEAM GENERATOR unrrs AND THE LIKE FiledSept; 4, i946 2 sheets-she??? lN ENTOR Jail/V PYLE 'ATTORNEYS PatentedMar. 14, 1950 UNITED This invention relates to improvements in tubularair preheaters such as the preheaters used in connection with largesteam generator units.

In large steam generator is usually built as a part positioned that thehot combustion gases from the upper part of the unit pass over into thetubes of the air preheater and pass downwardly through the tubes of theair preheater in heat exchange with air passing around the tubes, whichis prereplacement of lower tubes is necessary in the heated for use inthe generator. It has been found expedient in the case of large steamgenerators to build the airpreheater in two sections one above theother. In such practice each secfeet or more in length,

or otherwise secured in tube sheets. The two sections are commonlconstructed alike and one section set above the other in spaced relationso between the two adjacent sections.

One of the difiiculties in such constructions is that in order to makerepairs in the lower section of the air preheater it The primary objectof improved air preheaterfor section. In the preferred I provide an airpreheater as for example for a large steam generator unit with upper andlower tube sections. The lower the same number of tubes tion, but theyare of a diameter. such that tubes of the lower section may be passedthrough the tubes of the upper section. In this connection I arrange thesections so lower section are directly below the tubes of the STATESPATENT OFFICE TUBULAR AIR PREHEATER FOR STEAM GENERATOR UNITS ANDTHE-LIKE John V. Pyle, Briarclifi Manor, N. Y., assignor to Kennedy-VanSaun Mfg. & Eng. Corp., New York, N. Y., a corporation of DelawareApplication September 4, 1946, Serial N 0. 694,792

10 Claims. (Cl. 257-224) units the air preheater placements are made.

of the setting and so 5 with their ends rolled is necessary to remove Inthe drawings: the present invention invention. use in connection with onan enlarged scale.

form of my invention tube section includes that the tubes of the asthose in the upper tube section.

My improved tubular air preheater includes other features, objects, andadvantages which will be readily understood from the following detailedFor one thing the tubes of the lower section redescription thereof takenin connection with the quire much more frequent cleaning, to removesoot, than the upper'tubes, as well as much more frequent repair andreplacement.

upper section so that the smaller lower tube may be moved upwardlythrough the corresponding tubes of the upper section, When repairs orre- An air preheater constructed in accordance with the features of myinvention has been found to have a number of advantages over preheatersmade in accordance with known practices. example, I have found that muchless repair or new construction and that a greater efficienc is achievedin the transfer of heat from furnace gases to the air being preheated.cleaning of the lower tube section has also been tion is constructedwith vertically arranged tubes 16 found necessary. This increase ineficiency is quite unexpected since the use of smaller diameter tubes inthe lower section of the air preheater reduces considerably the heatexchange surface between the combustion gases and the that it ispossible for man to get in and work 20 air being preheated. However, itappears that the smaller tubes in the lower section have the function ofkeeping up a relatively high combustion gas velocity which results inthe maintenance of cleaner tubes and a higher rate of heat transthetubes in the upper section, that is in order 25 fer than in the case oftubes of the same diameter to remove tubes in the lower section. It hasalso been found that most of the tube difiiculties arise in connectionwith the lower section. Some of the reasons for this are not clearlyunderstood.

accompanying diagrammatic drawings forming a part of this application.

Fig. 1 is a broken vertical sectional view showtherefore is to providean improved tubular air ing a portion of alarge steam generator unitproprcheater which will be free of the difficulties and disadvantagesreferred to above.

Another object of my invention is to provide an vided with an airpreheater constructed and arranged in accordance with the features of myFig. 2 is a broken vertical sectional view showlarge steam generatorswhich is easy to repair ing a portion of the apparatus illustrated inFig. 1 and maintain.

I have discovered that most if not all of the difiiculties referred tomay be eliminated if the lower tube section is constructed of tubes ofsmaller diameter than those of the upper tube trating the method ofremoving and replacing tubes of the lower tube section of the heater.

Fig. 5 is abroken elevational view of the tubular preheater shownin'Fig. 1, looking from the left. Fig. 1 of the drawings shows a portionof a as the upper tube seclarge steam generator unit mounted in abuilding structure having a side wall It and a roof l2. The portion ofthe generator as shown includesv a water and steam drum M, in the upperpart of the setting, and a lower drum it, which are connected by longsteam generating tubes l8.

Fig. 3 is a broken horizontal sectional view taken on the broken line3-3 of Fig. 2.

Fig. 4 is a view similar to that of Fig. 2 illus- For Much less eter.upper and lower tube sheets 45 carrying regularly spaced heat exchangetubes 48.

The steam generator includes a firing chamber and other conventionalelements from which the combustion gases pass upwardily through achamber to heat the tubes i8 mounted in the furnace. These gases passaround the upper ends of the tubes l 8 into a tubular air preheaterwhich may extend substantially across the generator and which, as shown,comprises an upper tube section or bank 22 and a lower tube section orbank 24. As an example, these sections may be 20 feet or more in height.

The tube sections 22 and 24 are mounted in the steam generator settingin the usual manner and carried by the usual steel framework structureas, for example, by steel beams 26. The tubular air preheater isenclosed by the refractory walls as indicated and the two sections aremounted one above the other with anintervening space or chamber 28suitable for a man to enter for inspection, replacement, or forinstallation work. The side of the chamber 28 is provided with a row ofrefractory lined doors 30 which are removably by a block and tackle.

The combustion gases from the chamber 1 which pass over into the tubebank 22 pass downwardly through both sections of the tubular airpreheater and out through ducts 3t and to a stack or exhaust fan notshown. Any dust 1 settled out of the gases leaving the section M is Theair to be removed through a dust trap 31. preheated is introduced aroundthe tubes of the section 24 at the bottom of the setting and passedupwardly around bailies 38, through a by-pass duct shown in Fig. 5 andthen upwardly around the tubes of section 22. Baffles 42 causes the airto pass in a zigzag path across the tubes of the preheating section 22until it reaches the top of the section 22 where the hot or preheatedair is discharged through a duct M, and con.-

ducted to the combustion chamber of the generator unit by means notshown.

An important feature of my invention as pointed out above is theconstruction of the preheater section v22 with one size of tubes and thepreheater section 24 with tubes of a smaller diam- It will be noted thatthe section 22 includes The lower preheater section 24 comprises upperand lower tube sheets 50 in which are mounted tubes 52 having an outsidediameter slightly less than the inside diameter of the tubes 48, forexample, the tubes 52 may be one size smaller than the tubes 66.

This relationship is illustrated in enlarged scale in Figs. 2 and 3. Thetubes 48 and 52 may be rolled in their respective tube sets or weldedtherein. It will be noted that in accordance with the showing in Fig. 3the tubes 52 are mounted directly below and axially in line with thetubes 48.

In most generator installations the conditions are such that the tubesin the lower preheater section require more frequent replacing thanthetubes in the upper section. In the present in stance, thisreplacement of the tubes in the lower preheater section is made rathersimple since each lower tube may be removed directly through one of thetubes 48, that is, the tube directly above. Fig. 4 of the drawingsillustrates the manner in All.

which this may be readily accomplished. If an inspection of the tubes 52shows that some of them must be removed, they are cut away or otherwiseremoved from the tube sheets 50 after which a rope 54 is lowered throughthe tube d8 directly above and also through the tube 52 to be removed. Aknot or other suitable attachment 56 is applied to the end of the ropebelow the tube 52 and then the latter is raised through the tube 48 bythe rope 54 which may be passed through a sheave 58 as indicated. A newtube may be inserted in its proper place in the tubular section 24 byfollowing the foregoing procedure in reverse. If the rope 54 is a metalrope or cable, it may be used for holding the new tube while it is spotwelded in place. In making repairs the closures 3H and 32 are removedand a man enters the space below the section 26, through trap 31 or anend door 68 as shown in Fig. 1.

Many of the large steam generator installations are housed in buildingsso arranged that the use of Vertically spaced air preheater sections ofthe type of sections 22 and 24 are highly desirable from the standpointof repair and replacement of parts. While it is possible in making theoriginal installation to install sections 22 and 24 as units, thesection 24 being installed first, it is not usually possible in view ofall the other equipment such as flue ducts, air ducts, and variousauxiliary units, to remove a section as a whole. The present inventiontherefore provides a novel construction and procedure by which repairsand replacements of tubes in such a tubular air preheater may be made.The improved construction not only facilitates repairs to the lowersection of the air preheater, but also provides a preheater which ismore efiicient than present preheaters and which, because of the use ofsmaller tubes in the lower section, is less expensive.

From the foregoing description it will be understood that certain minorchanges in the construction and arrangement of the various parts may bemade without losing any of the advantages of the apparatus. Such changesare contemplated as coming within the spirit and scope of the appendedclaims.

What I claim as new is:

1. In a tubular air preheater of a steam generator unit adapted toreceive hot combustion gases and air to be preheated thereby, animproved air preheater comprising vertically arranged tube sections eachof which includes a bank of vertically mounted tubes for the passage ofhot combustion gases, said tube sections being spaced apart to provideaccess for repairs between sections and arranged so that the hotcombustion gases from the upper tube section pass downwardly through thetubes of the lower tube section, and the tubes of the lower tube sectionhaving an outside diam eter slightly smaller than the inside diameter ofthe tubes of the upper section, whereby the tubes of the lower sectionmay be removed through the tubes of the upper section for repairs andreplacements.

2. An air preheater as defined by claim 1 in which the tubes of thelower tube section are mounted in axial alignment with tubes of theupper tube section.

3. An air preheater as defined by claim 1 in which the air preheater ismounted within. the steam generator setting and includes a removableclosure above the upper tube section, a removable closure for the spacebetween the tube sections;

and a removable closure for the space below the lower tube section.

4. An air preheater as defined by claim 1 in which means is provided forpassing air to be preheated first around the tubes of the lower tubesection and then around the tubes of the upper tube section.

5. In a tubular air preheater for preheating air by heat exchange withhot combustion gases, a pair of upright tubular heat exchange sectionsmounted one above the other and each including a bank of long verticallyarranged tubes, the tubes of the lower section having an outsidediameter slightly less than that of the inside diameter of the tubes ofthe upper section and being arranged with their axes substantiallycoincident with the axes of the tubes of the upper section, wherebytubes of the 1ower section may be passed through tubes of the uppersection.

6. A tubular heat exchange unit comprising upper and lower tube bankscomprising upwardly extending tubes, means for mounting one bank oftubes directly above the other and in spaced relation with respectthereto, the tubes of the lower bank being mounted below and in linewith tubes of the upper bank and having an outside diameter slightlysmaller than the inside diameter of the tubes of the upper bank, wherebytubes of the lower bank may be moved through tubes of the upper bank.

7. In a tubular heat exchange unit comprising tubular sections arrangedone above the other and each having vertically arranged tubes, the tubesof the lower section being of an outside diameter slightly smaller thanthe inside diameter of the tubes of the upper section and arranged withtheir axes substantially coincident with the axes of the tubes of theupper section whereby tubes to be replaced in the lower section may bepassed respectively through vertically aligned tubes of the uppersection.

8. A tubular heat exchange apparatus including vertically arrangedtubular sections in which the tubes of the upper section are mounted inaxial alignment with the tubes of the lower section, and the tubes ofthe upper section having an inside diameter slightly greater than theoutside diameter of the tubes of the lower section, means extendingthrough a tube of the upper section adapted to be attached to a tube ofthe lower section, and means for elevating the tube to which said meansis attached through a tube of the upper section.

9. A tubular heat exchange apparatus as defined by claim 8 in which themeans extending through an upper tube comprises a rope.

10. In a tubular air preheater adapted to receive air to be preheatedand hot combustion gases for effecting preheating, the improvement whichcomprises an upright tubular air preheater including means at its upperend for receiving hot combustion gases, means at the bottom of thepreheater for discharging hot combustion gases, the tubular airpreheater including vertically spaced banks of vertical tubes the endsof which are mounted in tube sheets, the tubes of the lower bank havingan outside diameter slightly smaller than the inside diameter of thetubes of the upper tube bank and being mounted with their axes alignedrespectively with the axes of tubes of the upper tube bank, a removableclosure above the upper tube bank for access thereto, and a removableclosure for the space between the tube banks for access thereto.

JOHN V. PYLE.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Number Name Date 854,980 Bonus May 28, 19072,245,720 Rohrer June 17, 1941 2,418,815 Baver Apr. 15, 1947 FOREIGNPATENTS Number Country Date 234,923 Great Britain June 11, 1925 636,388Germany Oct. 7, 1936 86,349 Switzerland Oct. 16, 1920

